Polychlorophenylacetic acid containing an alpha chloro-substituent



United States Patent ()fi ice 3,134,808 Patented May 26, 1964 3,134,808 PGLYCEEOROPHENYLACETIC ACID CONTAIN- ING AN ALPHA CHLORO-SUBSTITUENT Edward D. Wei], Lewiston, Edwin Dorfman, Grand Island, and Jerome Linder, Niagara Falls, N.Y., assignors to Hooker Chemical Corporation, Niagara Falls,

N.Y., a corporation of New York No Drawing. Filed Mar. 9, 1959, Ser. No. 797,892 Claims. (Cl. 260-515) This invention relates to compositions of matter known as ring and side-chain chlorinated phenylacetic acids.

The present invention resides in new and useful substituted phenylacetic acids having the structure:

where n=zero or one. The physical embodiment of this concept has unique properties as a herbicide and chemical intermediate not logically predictable from the established properties of related compounds. Examples of such compounds are 2,4,5,artetrachlorophenylacetic acid; 2,4,5,01,zx-pentachlorophenylacetic acid; 2,3,4,a-tetrachlorophenylacetic acid; 2,3,4,a,a-pentachlorophenylacetic acid; and 2,3,6,a-tetrachlorophenylacetic acid.

The compositions of this invention may be prepared in the following manner.

Trichlorophenylacetic acids are chlorinated in the molten state or in an organic solvent resistant to chlorination (such as carbon tetrachloride). This reaction is advantageously accelerated by ultraviolet light or by catalytic amounts of organic peroxides. Alternatively, the compounds of the invention may be prepared by the chlorination of the corresponding phenylacetonitrile to introduce one or two chlorine atoms, as desired, into the a-position, followed by controlled hydrolysis of the nitrile to the acid or, if desired, to the amide or an ester of the acid by methods known to the art for hydrolysis of nitriles.

Another method of synthesis involved the direct chlorination of phenylacetic acid to simultaneously or consecutively introduce ring and side-chain chlorine. Still another process involves the reaction of the corresponding isomer of trichloromandelic acid with hydrogen chloride, thionyl chloride, or phosphorus chlorides. Using the last two reagents, the acid chlorides may be directly obtained.

The products of the invention are colorless crystalline solids soluble in most organic solvents and having only slight solubility in water.

Specific instances of preparations of compounds embodied by the generic concept of this invention are given in the following examples:

EXAMPLE I 2,4,5,a-Tetrachlorphenylacetic Acid Twenty-four parts by weight of 2,4,5-trichlorophenylacetic acid is warmed until fusion occurs and chlorine gas is then passed in under illumination by a 250-watt mercury vapor lamp. When the weight of the reaction mixture reached 29 grams, the mixture was recrystallized from carbon tetrachloride, giving a colorless crystalline product, melting point 157 C. to 159 C. The neutralization equivalent by titration with NaOH to form the sodium salt was 274 (theory for C H Cl O 274).

Analysis.-Calculated for C H Cl O total Cl--51.8; found for C H Cl O total Cl--52.3. Calculated Cl hydrolyzable by alcoholic KOH12.9; found Cl hydrolyzable by alcoholic KOH12.7.

EXAMPLE ll 2,4504,ot-Pentachlorophenylacetic Acid Chlorine gas was run into a solution of 24 parts of 2,4,S-trichlorophenylacetic acid in 300 parts of hexachlorobutadiene at 120 C. to 130 C. over a four-hour period. The solution was cooled to 20 C., then filtered and the crystals thus obtained washed with hexane. The yield was 22 parts of colorless product, melting point 164 C. to 166 C. The product after recrystallization from carbon tetrachloride melted at l68.5 C. to 169 C. Titration with 0.1-N aqueous sodium hydroxide (giving a water-soluble sodium salt) indicated a neutralization equivalent of 307 (theory for C H C1 O 308.3).

Analysis.CalCulated for C H CI O total Cl-57.5; found for C H Cl O total Cl--58.0. Calculated C1 hydrolyzable by alcoholic KOH23.0; found Cl hydrolyzable by alcoholic KOH22.9.

EXAMPLE III 2,3,6,a-Tetrachlorophenylacetic Acid Chlorine gas is passed into a refluxing mixture of 60 parts of 2,3,6-trichlorophenylacetic acid and 400 parts of carbon tetrachloride under illumination by a 250-watt mercury vapor lamp. When 9 parts of hydrogen chloride have been evolved, the solvent is concentrated to about one-quarter of its former volume, cooled, and filtered. The crystalline solid thus obtained melts at 156 C. to 158 C. The neutralization equivalent by titration with NaOH to form the sodium salt was 275 (theory for C H Cl O 274).

Analysis.Calculated for C H Cl O total Cl--5l.8; found for C H Cl O total Cl5l.4. Calculated Cl hydrolyzable by alcoholic KOH--12.9; found Cl hydrolyzable by alcoholic KOH12.7.

EXAMPLE IV Technical ltlixture of 2,3,4,a-, 2,4,5,0L- and 2,3,6,ot-

Tetrachlorophenylacetic Acid A melt of 100 parts of trichlorophenylacetic acid (about 40% 2,4,5-, 40% to 50% 2,3,6- and 10% to 20% 2,3,4-isomers by infrared analysis) was chlorinated at 120 C. under irradiation by a 250-Watt mercury vapor lamp. When one molar equivalent of hydrogen chloride had been evolved, the chlorination was stopped. The product was a gummy, colorless solid, observed neutralization equivalent 270 (theory for pure C H Cl O 274). The analysis of the product for chlorine showed that one molar equivalent of chlorine had been introduced. Refluxing the product with an excess of potassium hydroxide in methanol for three hours hydrolyzed the product with the release of one molar equivalent of chloride ion, proving that one chlorine was on the side-chain.

EXAMPLE V and a,2,3,4-Tetrachlorophenylacetamide Chlorine gas was passed into a technical mixture of 2293 parts of trichlorophenylacetonitrile (comprised of the correct nitrogen and chlorine analysis for C H Cl N.

To 1160 parts of 85% sulfuric acid at C. to

C. was added 2270 parts of this nitrile over minutes with stirring. Stirring was continued for 15 minutes longer, then the mixture was poured into several volumes of Water at 50 C. with stirring. The solidified amide thus obtained was filtered, washed with water, and dried to obtain a colorless solid.

Analysis.-Calculated for C H Cl N, total Cl-5l.7;

3 total N-5.l4. Found for C H CI N, total Cl52.8; total N5.0.

The compositions of the invention are useful as chemical intermediates. As contrasted with the chlorinated phenylacetics having only ring chlorines which are generally extremely unreactive, the compounds of this invention have reactive chlorine atoms on the side-chain which permit a great multiplicity of displacement reactions and, therefore, great utility as chemical intermediates. For example, 2,3,6,a-tetrachlorophenylacetic acid may be hydrolyzed to 2,3,6-triehloromandelic acid which has utility as a herbicide. Treatment with sodium methylate yields 2,3,6-trichloro-a-methoxyphenylacetic acid which also is a plant growth regulator. The compositions of this invention also have exceptional phytotoxic properties. In contrast to lower chlorinated phenylacetic acids which do not exert a significant killing action on plant foliage, the new compounds of the invention do exert powerful killing action on application to the foliage of plants and are, therefore, useful as outstanding rapidacting herbicides having residual activity. This type of herbicidal activity is surprising and unexpected, since the lower chlorinated phenylacetic acids are either substantially inactive or, as in the case of 2,3,6-trichlorophenylacetic acid (which is the subject of our copending application), act principally through the soil and by root uptake and are consequently very slow-acting herbicides. An unexpected and important advantage of the compounds of the invention is their fast rate of weed killing action.

The following example illustrates the herbicidal utility of the compositions of this invention.

EXAMPLE VI In representative experiments, the products of Examples II and III were sprayed at the rate of eight pounds per acre in an aqueous emulsion (using three parts of xylene and one part of Atlox 3335, a commercial nonionic emulsifier, per one part of active ingredient) on a mixed natural population of ragweed, lambsquarters and mustard. Both compounds caused severe foliar burns and twisting within a day, resulting in the death of the plants within a week. By contrast 01.,0t-dlChlOI'OPh6l'lY1- acetic acid, 2,4,S-trichlorophenylacetic acid and 2,3,4- trichlorophenylacetic acid produced substantially no effect. The sodium salts of the acids of Examples II and III above produced similar results.

EXAMPLE VII Use of 2,4,5,a-Tetrachlorophenylacetic Acid as Herbicide An area seeded with corn, wheat, mustard, pigweed and chickweed was sprayed pro-emergence with eight pounds per acre of 2,4,5,a-tetrachlorophenylacetic acid as the sodium salt in aqueous solution. After two weeks, the corn and wheat were found to have germinated and grown normally, while the mustard, pigweed, and chickweek were completely controlled. A comparison experiment at the same rate with 2,4,S-trichlorophenylacetic acid showed substantially no weed control.

The compositions of the invention may be converted to salts, esters, and amides in which form they also may be used as chemical intermediates and herbicides. These compounds may also be incorporated into mixtures with other herbicides as, for example, the hormonal phenoxyaliphatic acids, sodium chlorate, sodium trichloroacetate, sodium dichloropropionate, and the N-pheny1-NN'- 'dialkylurea herbicides together with formulation adjuvants of the type known to the herbicide art. A representative formulation of this sort is:

Parts by weight Sodium 2,4,5,a-tetrachlorophenylacetate Sodium 2,3,6,ot-tetrachlorophenylacetate 30 Sodium 2,4-dichlorophenoxyacetate 5 Sodium tripolyphosphate (sequestering agent) 20 The use of mixed isomers is generally preferred for economic reasons. In some cases the activity of mixtures of the compounds of the invention with each other or with other herbicides as named above appears to be greater than additive.

From the foregoing, it is obvious that certain salts including the alkali metals, the alkaline earth metals, ammonium, amine salts, or the organic ester such as methyl, ethyl, propyl, isopropyl, lauryl, glycol, chloroethyl, phenol, butoxyethyl, and the like, and amide derivatives of the acids of this invention may be more advantageously used under particular circumstances. The use of such derivatives or salts does not depart from the spirit of this invention, since field conditions or uses may require using a derivative or salt rather than the acid per se.

In determining whether it is advantageous to use in the field any of the aforementioned derivatives or salts of the acids of this invention rather than the acid per se, one determines the field conditions and selects the particular derivative or salt having the required characteristic to meet such conditions.

These derivatives and salts and the acid are generally effective when applied in quantities of about one-half pound per acre or more and, for ease of application, any conventional diluent such as clay, wood flour, fullers earth, vermiculite, or liquid carrier such as xylene, kerosene, alcohols and ketones or other carrier may be used, depending on the economics and distribution requirements. Formulations may contain emulsifying agents such as sorbital laurates, wetting agents such as sodium alkyl aryl sulfonate and sodium alkyl sulfate, and carriers in accordance with the well-established practices in the herbicidal field. Combinations of this herbicide with other known herbicides or compositions for controlling the growth of vegetation and plants to obtain desirable combinations and properties are within the spirit of this invention.

The examples of the compositions of our invention, and methods of preparing and utilizing them which have been described in the foregoing specification, have been given for purposes of illustration, not limitation. Many other modifications and ramifications will naturally suggest themselves to those skilled in the art, based on the disclosure of our basic discovery. These are intended to be comprehended within the scope of our invention.

We claim:

1. A composition selected from the group consisting of 2,3,4,ot-tetrachlorophenylacetic acid; 2,3,6,ot-tetrachlorophenylacetic acid; 2,4,5,ot-tetrachlorophenylacetic acid; 2,4,5,at,rx-pentachlorophenylacetic acid; the alkali metal salts; the alkaline earth metal salts; the ammonium salts; and the amides of said acids.

2. 2,4,5,a-tetrachlorophenylacetic acid.

3. 2,3,4,a-tetrachlorophenylacetic acid.

4. 2,3,6,oz.-tetrachlorophenylacetic acid. 5. 2,4,5,oz,ot-pentachlorophenylacetic acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,290,401 Witman July 21, 1942 2,551,674 Hillyer et al. May 8, 1951 2,695,840 Leppla Nov. 30, 1954 2,705,195 Cupery et al. Mar. 29, 1955 2,708,624 Denny May 17, 1955 FOREIGN PATENTS 573,664 Great Britain Nov. 30, 1945 661,499 Great Britain Nov. 21, 1951 OTHER REFERENCES Beilstein: vol. IX, page 450 (1926).

Thompson et al.: Antibiotics and Chemotherapy, vol. 3, pages 399-408 (1953).

Harvey et al.: Chem. Abst., vol. 49, col. 14671 (1955). 

1. A COMPOSITON SELECTED FROM THE GROUP CONSISTING OF 2,3,4,A-TETRACHLOROPHENYLACETIC ACID; 2,3,6,A-TETRACHLOROPHENYLACETIC ACID; 2,4,5,A-TETRACHLOROPHENYLACETIC ACID; 2,4,5,A,A-PENTACHLOROPHENYLACETIC ACID; THE ALKALI METAL SALTS; THE ALKALINE EARTH METAL SALTS; THE AMMONIUM SALTS; AND THE AMIDES OF SAID ACIDS. 